An image forming apparatus which superimposes tone images of different colors to provide a color image needs alignment control for controlling the positional relation between the toner images of different colors and image quality maintenance control for controlling the density of each color.
For example, when the time required for alignment control and image quality maintenance control at the time of warm-up of the image forming apparatus becomes longer, there is a risk that the user's waiting time before the start of print may become longer. On the other hand, when a scanning sensor for an alignment pattern and a scanning sensor for an image quality maintenance pattern are provided in order to reduce the waiting time, there is a risk that the manufacturing cost may increase.
Thus, it is desired that an image forming apparatus should be developed in which the time required for alignment control and image quality maintenance control is reduced while restraining the manufacturing cost.